Mechanical bonding lock



May 28, 1953 r R. D. HETHERINGTON 3,091,578

MECHANICAL BONDING LOCK Filed June 19, 1961 United States Patent O 3,091,578 MECHANICAL BNBING LOCK Robert D. Hetheriugton, La Crescenta, Caiif., assigner to Electro-Uptical Systems, Enc., Pasadena, Calif., a corporation of California Filed June 19, 1961, Ser. No. 118,161 3 Claims. (Cl. 21M- 16) This invention relates generally to the fabrication of a structure by plating methods, and more particularly, to a method and means by which thin layers of plating built up in interrupted succession during the fabrication of a structure are `securely locked together.

It is well known that thin-walled structures can be produced by electrodeposition of adherent metallic coatings on the surfaces of suitably prepared forms, such as negative molds, matrices, or mandi-els. The forms, which can be made from metal, wax or plastic, provide the proper shapes for the metal layers deposited on the surfaces thereof.

In a typical example, a layer of metal is deposited on a flat base. A form is then placed over a portion of the fiat metal surface, and an additional layer of metal is deposited on the form and the surrounding base layer. The structure thus built up is one having a base and an integral contoured shell projecting therefrom.

To form a unitized structure as above described, it is essential to obtain a strong bond between the contacting portions of the two metal layers. However, in interrupting the electroforming process to properly position the form, the thin base layer is subjected to oxidation and, of course, the accumulation of dust and grime thereon. As a result, blistering between the layers, and peeling of the second layer, will occur.

To avoid these undesirable results, it is necessary to suitably treat the base layer, as by chemically cleaning and pickling it, so that the newly deposited metal Will be bonded securely to the contact surface areas thereof. Further, it is necessary that such preparation for plating or electrodepositing be done carefully and thoroughly so that the base layer is completely free of all foreign substances such as grease, and compounds such as oxides or suliides.

Such preparation and treatment of a thin metal layer is clearly time-consuming and costly. And, despite such care and expense, it is not unusual that portions of the thin layer are destroyed. In this connection, a chemical cleaning agent for removing oxidation necessarily removes some of the metal. Since it is not possible to precisely control the cleaning action over all portions of the metal surface, and since the metal surface so treated is extremely thin, portions of the surface are occasionally destroyed altogether.

It is an object of my invention to provide a means and method for obtaining a tight bond between a coating of plating and another coating of plating subsequently deposited on the surface of the first coating by a plating process, without first having to prepare the surface as by cleaning and pickling the same.

Another object of this invention is to provide, for film-like layers of metal that have contacting surface areas, a method and means for causing said layers to be mechanically self-locking.

A further object of this invention is to provide, for a layer of metal to be supported on a layer of oxidized metal, wherein portions of the two layers are spaced with respect to each other, means for securing said layers together without chemical treatment of either.

Briefly, and in general terms, the foregoing and other objects are accomplished by initially providing a ridgeforming filament, such as a small wire, chain, or the like, arranged in a desired contour pattern on a plating base,

3,091,578 Patented May 28, 1963 ICC depositing a comparatively thin layer of plating of required thickness on the base and over and around the filament, thereby forming a thin sheet structure which includes a prominent, or upstanding, portion. At any subsequent time, another comparatively thin layer of plating is deposited over at least the part of the first layer which includes the prominent portion.

The above and other objects and advantages of my invention will become apparent from the following description taken in conjunction with the accompanying drawing of illustrative embodiments thereof, in which:

FIGURE l is a perspective view of a dome-like mirror structure, showing a dome member with a rim locked to a base plate by an upstanding ridge portion;

FIGURE 2 is a fragmentary and enlarged sectional view of an edge portion of the structure of FIGURE l, illustrating the construction of the ridge portion and the manner in which the parts are locked together;

FlGURE '3 is a fragmentary plan view of a structure having two plating members mechanically locked together by means of a wire and chain combination;

FIGURE 4 is a sectional view taken along the line 4--4 of FIGURE 3, illustrating the interlocking construction of the parts;

FIGURE 5 is a fragmentary plan View of a structure having a generally curving plating member mechanically locked to a plane plating member by two different locking elements; and

FIGURE 6` is a sectional view of the structure shown in FIGURE 5, as taken along the line 6--6.

A mirror structure 10 utilizing a mechanical bonding lock according to my invention is shown in FIGURE 1. The mirror structure 10 includes a fiat, plane disc 12 having a mirrored lower surface 14, and a dome-shaped member .16 bonded to the back, or upper surface of the disc 12. The dome 16 has a circular opening 18 which permits access to the interior of the dome 16 after it has been bonded to the disc 12.

T he mirror structure 10 may, for example, be produced by electroforming. Referring to FIGURE 2, a fiat base 20, which can be of glass, is coated on its upper surface with a very thin film of silver 22. The silver film 22, which is a circular film of the diameter desired for the disc 12, can be sprayed on the upper surface of the base 20, or it can be applied by vacuum evaporation. The silver iilm 22 is only a few millionths of an inch thick, and provides a reflecting surface.

The base 20 is effectively made conducting, as by suit- -able electrical connections (not shown) to the silver film 22. A filament, such as a Wire ring 24, is then placed lon top of the silver film Z2, The diameter of the wire ring 24 is a little less than the diameter of the silver film 22, and the wire ring 24 is positioned near the edge of the silver film 22, `as indicated in FIGURE 2. As is also shown in FIG. 2, the under surfaces of wire 214 angle down toward the base to form dove-tail recesses between the Wire and the silver-coated base. A firs-t layer of plating 26 is then electrodeposited against the wire ring 124 and the upper surface of the silver film 272i. The deposited metal iiows around the wire, and thus creates a layer of plating that has an integral upstanding ridge, wherein the transitions between the plating on the wire and the flat portions of the layer 26A are sharply Vconvergent crevices. Also, these crevices are angularly spaced more than a factor which, as will be seen, aids the desired locking of a seco-nd layer to the first. Stated differently, the surfaces of Wire QA- and base 20 form sharp discontinuities at the points Iof contact therebetween, the discontinuities having the configuration of acute tangles, as is clearly shown :in FIG. 2. Accordingly, when the first layer of plating is deposited, it has the configuration of the surfaces of the :easily shaped to various contours.

wire and base combined and, therefore, includes the aforesaid discontinuities.

After a desired thickness of the first layer of plating 26 is obtained, the dome 16 (FIGURE l) is formed. To thisend, a dome-shaped mandrel or wax form 2S is then positioned Within the wire ring 24, and a second layer of .plating 30 is electrodeposited over the plated wire ring V24, the outer annular surface of the rst layer of plating 26,.and the surface of the wax form 2S. To aid in forming the metal layer on the wax form 2S, the surface of the wax form 28 is coated with a very thin layer of graphite, for example, so that the surface of the form 28 is made conducting.

As shown in FIGURE 2, the metal forming the second vlayer of plating 30 is deposited on all exposed portions of the plating on the 4ring 24. Thus, the metal of the second layer 30 also has transitions that are sharply convergent crevices. Still further, these crevices are also angularly spaced more than 180. Thus, the portion of the second layer 26, 30 that overlays the twire is in the form of a sleeve which has a circumference greater than 180 but less than 360. Stated dilerently, the deposited metal that forms lay-er 30 also ows into the above-said dove-tail recesses. A mechanical lock is thus obtained, because the second layer o-f plating 30 literally grips the prominent, plated wire ring 24 and the first layer thereon.

To get the desired locking action, the wire diameter of the ring 24 should be several times the thicknesses of the metal layers. For example, in the process of electrofOrming, the structures produced have relatively thin members, e.g., the thicknesses of the metal layers may be of the yorder of twoor three-thousandths of an inch. If the Ilayer of lplating 26 is, Vfor example, .00:2 inch thick, the wire ring 24 may have a wire diameter of approximately .0110 inch, or live times the thickness of the layer of plating 26. It is to be understood, of course, that the dimensions given are merely examples, and are not intended to limit the scope of my invention.

'Where, as in the structure lof FIGURE l, .the one metal 'member is upstanding from the other, the locking ridge `is desirably located nea-r the junction line of the two members. For example, in FIGURE 2, the wire ring 24 is located along the line 4along which the second layer of plating 30 contacts the first layer of plating 26. However, .if lthe contacting surface areas of the layers of plating 26 and :30 extend a substantial distance beyond the initial junction point of layer of plating 30 and the layer of plating 26, a second wire ring, Ysimilarto the wire ring 2-4 but having a larger diameter, can be located concentrically to the wire ring 24, so that the outer edges of the two layers vofplating Z6 and T30 will be llocked together by the result- 'ing outer ridge and prevent peeling of :the layers 'of plating from the outer edges.

A small link chain can be `used in place of the wire ring 24. The chain can be a silver jewelry chain, for example, having links which are approximately %4 inch long. A link chain has the -advantage in that it can lay relatively flat `on the base 20, and additionally :can be tAlso, the links provide a great number of crevices -into which the deposited plating may diow to create the desired grip. In `FIGURE 3, a chain 32 and wire 34 are used as locking elements between two layers of plating 36 and 38. The chain and wire are, of course, not shown in correct proportional sizes.

Referring now to FIGURE 4, the chain 32 `and wire 34 are first placed on top 'of a glass base 40 which has been 4made conducting by coating it fwith graphite, for example. A tirst layer of plating 36 is Vthen electrodeposited over the chain 32, wire 34 and on the surface of the base 40. A plastic block 42 -is 'then lproperly positioned on top -of the rst layer of plating 36, and a second layer of plating 38 -is deposited over the plated surfaces of :the chain 32 and wire 34, and also on the conductively treated sides of ithe plastic block 42. The second layer of plating 38 is thus mechanically locked to the first layer of plating 316, in the same manner as the layers r26, 30 of FIGURE 2.

It should be noted that the electroforrning process employed to produce the plating structure is entirely conventional, and details of its opera-tion have been omitted from this description. However, suchdetails may be obtained from an article by Richard C. IBarrett entitled Nickel Plating From the Sulfamate Bath, pages 169- of Proceedings `of the American Electroplaters Society, published lin 1954. Detailed electroforming information may also be obtained from Patent No. 2,318,592 entitled Electrodeposition and issued to Marti-n E. Cupery on May 11, 1943. It should also be noted that vthe second layer of plating 38 can be deposited and formed at a much later time `following the formation of the iirst layer of plating 36, and possibly after some work has been done on the structure of the first layer of plating. The mechanical bonding lock provided by my invention eliminates the need for a strong lchemical bond, and therefore elirninates the time-consuming and metal-deteriorating cleaning and pickling treatment heretofore required prior to the deposit of a second layer of plating.

While a at plating base vhas been shown, 4it is clear that my invention is not limited in this respect. For example, the top sur-face of the base can be-curved. In such a case, the locking element is also curved to conform with the contour of the base. Suitable means, such as nonconducting tabs, can be used to fasten down the locking element at points which will not affect the proper depositing of plating. There are, of course, many ways and means for securing the locking elements in place on any basesurface.

FIGURE 5 shows a structure formed from two plating members 44 and 46 which lare bonded and mechanically locked -together by means of locking elements 48 and 50. As can be -seen in FIGURE 6, which 4is a sectional View taken along the line 6-6 as indicated in FIGURE 5, the plating member46 has an upright curved plane section. The locking element 48 is provided close to the vertical curvingsection Vof the plating member 46, land the locking member 50 is located close to the horizontally outer edge of the plating member 46. To prevent peeling between plating members at the outer edge, it may be necessary to have a locking element close to the edge, and for this purpose, a straight Iwire can be used as a locking element 50. It is noted that a straight wire, properly treated, can be pulled outafter fabricating the structure, and the parts Would still be locked together.

In order to provide a locking member close to the junction edge near the vertical section of the plating member 46 and the plating member 44, the locking member 48 is curved, as indicated in FIGURE 5, to follow the curvature of the vertical section of the plating member` 46. If the curvature is high, it becomes difficult to shape or arrange the wire or chain to follow the curvature -of the plating member 46 closely. A flexible locking element can be derived from a thread, string or cord, which has been suitably coated with wax and graphite, or any other conducting compound. Thus, a highly -lexible locking element can be obtained 'to follow the curvature of the vertical section of the plating member 46 very closely so that a good mechanical lock is obtained.

The vlocking mem-ber has been generally described as la prominent locking structure produced on a Afirst layer of plating. The important point is that it is a structure which provides sharp crevices and corners for the second layer of plating to grip mechanically. The prominent locking structure includes, of course, depressions `or recesses having sharp crevices and corners. Such depressions or recesses are inverted, prominent locking structure, and can be produced by depositing a lrelatively thick first layer of plating .which nearly covers a locking wire, -for example, and then removing the same to leave a prominent locking recess.

In the construction of structure by plating methods, -the electroforming process is the most practical and commonly used. Accordingly, the foregoing description has been made with reference mainly to this process. My invention, however, is not limited to the electroforrning process, -but is applicable and useful in yall plating methods for the construction of articles and structure. "Further, it is to be understood that the particular embodiment of my invention described above and shown in the drawings is merely illustrative of, and not restrictive on my broad invention, and that various changes in design structure and arrangement may be made without departing from the spirit and `scope of the appended claims.

I claim:

1. A method for `contour ridging and, in successive platings, plating a flat base in a manner to insure interlocking the platings to each other and to the base, said method comprising the steps of: laying on a iiat base a planar ridgeforming filament having va height greatly in excess of the final thickness of ythe platings and being of such a crosssection as to provide under surfaces angling down to said base -to provide dove-tail recesses between -the filament and the base; contouring said filament to be of the contour desired for the ridge; prime electroplating said base and said filament, such plating entering the dovetail recesses under said filament; and further and Ithereafter separately electroplating said plated base and said plated iilament, such second pla-ting also entering the dove-tail recesses under said lament.

2. A method according to claim 1 wherein said lament is a Wire.

3. A method according to claim 1 wherein said filament is a link chain.

References Cited in the ile of this patent UNITED STATES PATENTS 

1. A METHOD FOR CONTOUR RIDGING AND, IN SUCCESSIVE PLATINGS, PLATING A FLAT BASE IN A MANNER TO INSURE INTERLOCKING THE PLATINGS TO EACH OTHER AND TO THE BASE, SAID METHOD COMPRISING THE STEPS OF: LAYING ON A FLAT BASE A PLANAR RIGID-FORMING FILAMENT HAVING A HEIGHT GREATLY IN EXCESS OF THE FINAL THICKNESS OF THE PLATINGS AND BEING OF SUCH A CROSS-SECTION AS TO PROVIDE UNDER SURFACES ANGLING DOWN TO SAID BASE TO PROVIDE UNDER SURFACES ANGLING THE FILAMENT AND THE BASE; CONTOURING SAID FILAMENT TO BE OF THE CONTOUR DESIRED FOR THE RIDGE; PRIME ELECTROPLATING SAID BASE AND SAID FILAMENT, SUCH PLATING ENTERING THE DOVETAIL RECESSES UNDER SAID FILAMENT; AND FURTHER AND THEREAFTER SEPARATELY ELECTROPLATING SAID PLATED BASE AND SAID PLATED FILAMENT, SUCH SECOND PLATING ALSO ENTERING THE DOVE-TAIL RECESSES UNDER SAID FILAMENT. 